Wavelength-Division-Multiplexing (WDM) Transmission systems provide scalable capacity by adding additional wavelength channels as capacity demands grow. In addition, well-known multiple protocols like SONET, Fiber Channel, Gigabit Ethernet (GbE), and ESCON can be transmitted over the same fiber by putting each protocol on a separate wavelength. While this method provides flexibility, it does not efficiently use the bandwidth provided by the wavelength. For example, GbE only utilizes 1.25 Gb/s of a 2.5 Gb/s or 10 Gb/s WDM communications channel, and the ESCON even only utilizes 200 Mb/s, one-fiftieth of the bandwidth provided in a 10 Gb/s wavelength.
Three main approaches have emerged that allow aggregating multiple communications channels into a single wavelength to increase bandwidth efficiency, while providing fixed bandwidth guarantees for each of the channels:                Mapping protocols into the SONET hierarchy and using SONET multiplexing to aggregate to the higher bit rate. For example, 100 Mb/s Fast Ethernet can be mapped into an 155 Mbps OC3 circuit, and 16 OC3's can be multiplexed into an 2.5 Gbps OC 48 SONET WDM link.        The new and still evolving Digital Wrapper standard (ITU G.709) can be used for multiplexing almost arbitrary communication channels onto a higher-speed link        Simple TDM (time-division-multiplexing) techniques can be used to aggregate multiple communications channels onto a single wavelength        
While the first two methods involve the use of complex SONET or SONET-like framing chips as well as a number of external chips and buffering to map Ethernet into the SONET or Digital Wrapper circuits, the latter method is an easy to implement and low cost solution. A problem with the latter method is that TDM interleaving of packet signals leads to a nonstandard format, making it difficult to interface with existing transport equipment.
There is a continuing need for a data transport arrangement that would allow aggregating multiple communications channels into a higher bit rate link to increase bandwidth efficiency, without compromising the underlying channelized, guaranteed-bandwidth nature of the individual communication channels.